Junior dos Santos can finally resume his UFC career after a long investigation by USADA into tainted supplements that doomed the former heavyweight champion from competing since last May.

The situation started when the UFC was notified that dos Santos had failed a drug test last August, which cost him a fight against fellow heavyweight Francis Ngannou as he was pulled from the event where they were scheduled to compete.

Dos Santos immediately proclaimed his innocence regarding the positive drug test as he was always a staunch advocate in support of USADA and the UFC’s anti-doping policy.

On Monday, USADA officials revealed that Dos Santos was one of three UFC athletes who fell victim to ‘compounding pharmacies’ in Brazil giving them tainted supplements. Unlike regular drug stores that receive products directly from the manufacturer, compounding pharmacies receive ingredients and mix medications or supplements in house while promising to provide a better environment to avoid crossover or contamination.

That wasn’t the case with the compounding pharmacies that sold supplements to Dos Santos was he was a victim of those tainted products, which ultimately resulted in his positive drug test.

“I’m relieved that this nightmare is finally over and that we were able to determine what happened and where the prohibited substance found in my sample came from,” dos Santos wrote in a statement released on Monday. “Like I’ve always said, I’m a clean athlete. The most important thing now is that I can go back to earning my livelihood. I want to get back inside the octagon as quickly as possible. Back to business.”

According to dos Santos’ team, the fighter has been using supplements prescribed to him by his endocrinologist for more than five years without any problems coming up previously. Dos Santos cooperated fully with USADA once his testing sample was flagged but the investigation was hit with several delays outside of his or USADA’s control according to his team.

The situation was particularly tough on dos Santos considering how often he’s spoken out against the use of performance enhancing drugs in mixed martial arts.

Add to that, dos Santos has now been out of action for nearly a year since his last fight against heavyweight champion Stipe Miocic in May 2017.

Dos Santos also had to accept a six-month suspension from USADA, although that time has already expired so he can book his next fight immediately.

“The process has been extremely frustrating for Junior, who has always supported anti-doping measures, always supported USADA, and always advocated for a clean sport,” dos Santos’ longtime attorney Ana Claudia Guedes said. “Junior was pulled from his planned October bout against Francis Ngannou and has not fought since his May 2017 title challenge against champion Stipe Miocic.

“While the reduced sanction of six months is less than the one year provided for a first violation of the UFC anti-doping policy, the practical reality of such a long investigation coupled with the difficulty of UFC heavyweight matchmaking means Junior will go nearly a year without a fight. It’s unfortunate, it has been very rough on Junior.”